With the constant development of the semiconductor technology, more and more functions are integrated onto a small sized wafer substrate, and the wires laid on the wafer substrate are denser and denser. The device with 65 nm wide wires has been successfully developed at present, and the device with 45 nm wide wires will be produced in large scale finally. With the gradual popularization and application of the fine pitch or ultra fine pitch lead bonding technology, the pitch between conducting wires or conductors becomes smaller and smaller, achieving 60-40 um, and even as small as 35-30 um within a few years in the future. As a result, a chip having the same size as before has more and more powerful functions nowadays.
The conducting wire welded on a wafer usually has the diameter of 25.4 um/20 um or even thinner e.g. 18 um. And the diameter of a corresponding welded gold ball is 32 um-50 um. Those connecting wires and gold balls must be firmly and reliably welded on a weld pad on a wafer substrate. The to-be-tested welded object is too small in size, therefore the test device must precisely align the welded gold ball to be tested, and generates no alignment bias during the process after the alignment before the termination of the test, so as to ensure the accuracy of the test result.
All known test devices have a basic structure provided with a horizontally placed or vertically placed force sensor, and an implemental push cutter used for contacting and positioning a plane attached by a to-be-tested welded object for testing shearing force. By contacting the plane attached by the to-be-tested welded object via the implemental push cutter, the position of the plane attached by the to-be-tested welded object in the Z axis direction can be sensed. The position is taken as a benchmark to determine the bottom of the to-be-tested welded object, and heighten by a preset height h, e.g. 3 um, relative to the bottom of the to-be-tested welded object; and then a relative movement is conducted for testing the shearing force, thus obtaining a repeatable welding strength test value.
The U.S. Pat. No. 6,078,387 discloses a mechanism realizing contact sensing: the mechanism is provided with a main body having a horizontal double-arm cantilever beam structure; one end of the double-arm cantilever beam is fixed on a fixing block, and the other end (free end) is connected with a moving block and a probe (namely the implemental push cutter in the present patent). The free end of the double-arm cantilever beam can move freely up and down under the effect of an air bearing. Firstly of all, a photoelectric sensor is utilized to sense the displacement generated when the probe fixed on the moving block at the free end of the double-arm cantilever beam contacts the plane attached by the to-be-tested welded object; then the compressed air supply is stopped to cease the effect of the air bearing, and the elasticity of the double-arm cantilever beam is utilized to fix the moving block on the fixing block, thus realizing positioning purpose.
According to physical common sense and geometry knowledge, when the free end of the cantilever beam displaces up and down relative to the fixed end, the free end will inevitably have a horizontal displacement at the same time. That is to say, the method employing a cantilever beam structure to realize contact sensing actually has the problem of horizontal offset between fixed positions before and after the contact, such as the offset P1 as shown in FIG. 4.
Supposing that the length of the cantilever beam is L; in order to realize the above contact, the free end rotates an angle a1 after contacting a target plane; and the endpoint of the free end of the cantilever beam moves from D1 to D2, in which case the free end of the cantilever beam will inevitably have a position offset P1. According to the triangle relationship, the corresponding relationships between the position offset P1 and the rotation angle a1, the included angle a2 between the connecting line of the two displacement points and the normal line, and the cantilever beam length L can be easily obtained as follows:B=2×L×Sin(a1/2)P1=B×Sin a2=2×L×Sin(a1/2)×Sin(a2)
The specific offset caused by a specific cantilever beam structure will not be discussed herein. However, it can be affirmatively determined that the contact positioning mode using a cantilever beam structure will result in the offset between fixed contact positions, and the horizontal offset P1 (as shown in FIG. 4) between fixed contact positions may result in the dislocation between the implemental push cutter and the to-be-tested welded object; and different contact forces will cause nonlinear change of the horizontal offset P1 between fixed contact positions, thus not facilitating the control of different contact forces.
FIG. 5 vividly shows the relative sizes and relative positions of the implemental push cutter and the welded gold ball from the relative movement direction during the shearing force test process of the welded gold ball which is a fine pitch or ultra fine pitch semiconductor product. As shown in FIG. 5, in a densely arranged welded gold ball array, because the welded gold balls are arranged densely, the gap between welded gold balls is very small. The implemental push cutter shall not offset along the horizontal offset P1 direction (FIG. 5) of the fixed position aligned before the shearing force test is conducted. The position offset may cause dislocated shearing to the implemental push cutter and the welded gold ball to be tested, that is to say, the welded gold ball may be sheared incompletely and two welded gold balls may be partially sheared, thus resulting in failed test results. The problem of horizontal offset of the fixed position shall be avoided during the shearing force test of the fine pitch or ultra fine pitch semiconductor.
As a matter of course, when the cantilever beam structure is used, the rotation angle can be controlled in a very small range with various methods, so that the horizontal offset P1 of the fixed position can be reduced but cannot be avoided. And when a greater contractor force is required to confirm the contact, a greater rotation angle a1 will certainly be required, in which case the offset P1 of the fixed position will greatly increase accordingly.
In order to solve the above problem, a Chinese patent CN201382828 discloses a shearing force test device, comprising a substrate capable of moving up and down and mounted with an elastomer having a free end capable of moving towards or away from the substrate, the free end being connected with a test head; wherein the elastomer has a horizontal symmetrical structure; the free end is located on the symmetric line of the elastomer having the horizontal symmetrical structure; a pressing mechanism for fixing the test head is arranged above the test head; a gap facilitating the vertical moving of the free end and the test head connected to the free end is arranged between the free end and the substrate; after the test head is accurately positioned, the free end closely leans against the substrate under the effect of the pressing mechanism to fix the test head. The shearing force test device properly solves the problem that horizontal offset will occur to the fixed contact position during the shearing force test process. However, the device still has the problem of front and back small swaying.